The effect of ultrasound on flap survival: an experimental study in rats

Ultrasound is commonly used by physical therapists, but there is no consensus regarding the most effective therapeutic dose for accelerating healing of open or closed wounds. Now, the effect of therapeutic ultrasound on the formation of new blood vessels in full-thickness excised lesions in the flank skin of adult rats has been assessed quantitatively using microfocal X-ray techniques.

To investigate this, 30 rats were divided into three groups of 10 animals: a control group and two treated with ultrasound groups. Random dorsal skin flaps were elevated on the rats. In the control group, no operative procedures agents were used. Of the two treated groups, group 1 were exposed to pulsed ultrasound (2 ms on, 8 ms off) at an intensity of 0.1 W cm(-2) SATA (frequency either 0.75 MHz or 3.0 MHz). Group 2 exposed to pulsed ultrasound (2 ms on, 8 ms off) at an intensity of 0.18 W cm(-2) SATA (frequency either 0.75 MHz or 3.0 MHz), respectively.

The areas of flap necrosis were measured in each group. The median lengths of flap necrosis of the groups were 79.3, 57.0, and 35.3 mm, respectively. There was a statistically significant improvement of flap necrosis in ultrasound-treated groups compared with the control group (group 2, p=0.001; group 3, p=0.001). Furthermore, there was less necrosis in the high intensity ultrasound-treated group than the low intensity-treated group.

Ultrasound may have an intensity-dependent effect to increase flap survival in random skin flaps.